Ministry of Agriculture, Food and Rural Affairs
What's the best method for drying-off dairy cows?
The basic goals of a good dry-off program for all cows remain the same-it should reduce mastitis risk and keep cows comfortable
One of producers' most frequently asked questions at any mastitis seminar is what is the best way to dry off a cow? Producers always want to know if cows should be dried off abruptly, as was recommended by researchers in the past, or more gradually, as is frequently done on many Ontario farms. Determining the dry-off method that works best on a farm isn't easy since many other factors can impact the rate of mastitis occurring in cows in early lactation. Controlled research can help distinguish important features of the dry-off method.
Impact of teat closure timing
Recent information emphasizes the importance of reducing milk production before dry-off. In a study of 300 cows in five herds, Guelph researchers found rapid teat closure strongly reduced the likelihood of new mastitis infections occurring during the dry period. The variability in the rate of teat-end closure between cows was remarkable. By examining the teat ends of cows weekly for six weeks after dry-off, researchers found more than 50 per cent of teat ends closed during the first week, but almost 25 per cent remained open as long as six weeks after dry-off. The level of milk production before dry-off was the most important factor influencing the speed of teat closure. Teat closure was faster in lower-producing cows. Among cows milking less than 21 kilograms per day, 70 per cent of teat ends closed in the first week. Only 43 per cent of teats closed in cows with high milk production.
This research clearly linked the importance of decreasing milk production for reducing new mastitis infections by milk production's impact on teat-end closure.
A cow's milk production can most readily be reduced through diet changes. Reducing either dry matter intake or the energy density of a cow's ration has been shown in research and through practical experience to reduce milk production before dry-off.
Changing milking frequency before dry-off also reduces milk production, but can impact mastitis. In an Ohio study of 285 cows in five herds, mastitis rates were compared with cows milked two or three times daily to the end of lactation and those milked once daily for seven days before dry-off. The once daily milking reduced milk production by about 30 per cent so cows were producing roughly 13 kgs by dry-off compared with 18 kgs in herdmates in the continuous milking group. For cows ending their first lactation, gradual dry-off lowered the mastitis rate in the next lactation by 3.5 times, but among multiparous cows it increased it by 2.8 times. It appears the benefit of reduced milk production in older cows was masked by other mastitis-causing factors unique to this group. Dry-off method may not matter as much if other mastitis risks are present in a herd.
Determining optimal milk production
To follow up on the first project, researchers conducted a second study, which was just published. This time, researchers studied 428 cows drying off in eight herds. Milk production levels before dry-off had a strong impact on mastitis in the following lactation; cows with high milk production had more. Dry-off method did not affect mastitis, however, the impact of the dry-off method varied between the eight herds. In some herds, the dry-off method was associated with more mastitis while in other herds it was not.
The study showed the same dry-off program could not be recommended to all herds. Combining the results from both studies, the Ohio researchers suggest a dry-off method may need to vary by herd and, perhaps, for groups of cows within the herd to be fully effective. More work is needed to identify differences in mastitis risks between herds to determine whether abrupt or gradual dry-off methods are best in a given situation.
Determining the optimal level of milk production to target at dry-off to reduce mastitis is still in the works. The Guelph researchers showed teat ends closed faster and mastitis was reduced when cows produced less than 21 kgs of milk. The Ohio researchers found reducing milk production to about 13 kgs mainly reduced mastitis in first-lactation cows and not in older ones. In research from British Columbia, cows milking about 24 kgs before dry-off dropped in milk production to 14 and 10.4 kgs in abrupt and gradual groups. Among these cows, about three times more cows leaked milk in the two days following the last milking in the abrupt group. Since milk production is highly variable, it will likely be very difficult to come up with a volume of milk that works in all situations. In spite of this, it has been shown reduced milk production before dry-off protects against mastitis in the next lactation. Finding the best way to reduce milk production before the last milking is a good herd strategy to lower mastitis risk.
Mastitis is not the only important outcome of a dry-cow program-cow discomfort also needs to be considered. New Zealand researchers studied cows milked once or twice daily and fed their regular ration or a restricted diet to see if they would show discomfort at dry-off. All cows in this study had less than 10 kgs of milk on the last day of milking before dry-off. No change in behaviour was noted in either the once- or twice-daily milked cows. Restricting dry matter fed to 8 kg instead of 16 was more effective in reducing milk production than reducing milking frequency. Cows fed their full ration before dry-off laid laterally more often but showed no other signs of positioning or changes in lying time that showed discomfort. The restricted-diet cows vocalized more suggesting they were hungry. The authors suggest while the dietary restrictions reduced milk production effectively, it might be better to feed unrestricted amounts of a lower-quality, lower-energy diet to reduce milk production and mitigate hunger.
Drying-off cull cows
Although much research has been done and continues to be done on the best ways to dry off cows at the end of lactation, there is little that has been done on the best ways to dry off cows that may be leaving the herd but not completing lactation. Cows are removed from dairy herds at different days in milk for various reasons. Sometimes removal is due to low production but may also be for health problems, such as lameness, mastitis, injury or failure to conceive. These removals may occur when milk production is higher than at the end of lactation. Removal often involves transporting a cow from the farm to an auction barn where she can be sold. Dairy cows may be held at sales barns or collection yards for varying lengths of time and may travel for several days to reach their final destination. Most cows sold at the larger Ontario sales barns will be exported to the United States. In each of the last five years, more than 200,000 cows have crossed the border annually to slaughter plants in states such as Pennsylvania and Wisconsin. Cows are not milked after leaving the farm. Those with large udders are more likely to incur udder and teat injury, or mastitis, during transport or in group housing. Preparing cows for this movement should be part of routine cow management. These cows would benefit from a strategic dry-off program.
Most producers already know a certain cow in their herd is high on the culling list, and may have prior knowledge of when that removal will occur and where that cow will go. A few producers report they successfully separate cows seven days before their removal dates. Then, depending on a cow's level of production, the producer will either reduce milking frequency or cease milking, and feed the cow mostly dry hay before transport.
Producers are sometimes concerned drying off cull cows could trigger a flare-up with mastitis and make these cows unfit for transport or slaughter. There is no research directly addressing this question; however, research on standard dry-off procedures can help. In the studies of dry-off programs, cows were dried off at varying levels of milk, with many having pre-existing udder infections, but with no reported cases of clinical mastitis. In the New Zealand study, cows were more likely to get subclinical mastitis infections if they remained on the higher rate of feeding; these infections were almost all environmental streptococci. These cows had no increase in new mastitis infections due to the reduced milking frequency. In the Ohio research, no difference in mastitis was observed with changes in milking frequency. The Guelph research showed how important reducing milk production was to facilitate teat-end closure. It seems reasonable for cows being removed from the herd, just like those dried off at lactation end, reducing milk production will protect from mastitis. A change in milking frequency does not cause existing infections to flare-up. More research could help, but for now it seems reducing milk production in cows that will be culled by changing their rations is a good recommendation, and provided teat ends are kept clean, infection risk will not increase when milking frequency is reduced.
The proAction animal care module requires producers to have a standard operating procedure (SOP) for removing cows from the herd. While not a required element in proAction, it seems reasonable to include these two practices in the SOP: reducing the energy density in feed and the frequency of milking starting seven days before cows leave the herd. Further research on dry-off protocols for cull cows would also be a good idea.
Reducing feed, milkings may reduce mastitis risk
The basic goals of a good dry-off program for all cows remain the same. A dry-off program should reduce mastitis risk and keep cows comfortable as they transition to a dry state. This prepares them for subsequent lactation, or it may alleviate discomfort and risk for cows leaving the herd. Reducing the nutrient density of rations, while maintaining feed volume, is the best way to reduce milk production. Reducing milking frequency may ease discomfort, although more information is needed. However, milking frequency reductions can be done without increasing mastitis risk, provided teat ends are kept clean and dry.
This article was originally published in the Milk Producer magazine.
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